1. Field of the Invention
The present invention relates to a beamwidth adjustment device, and more particularly, to a beamwidth adjustment device for adjusting a beamwidth formed by a feedhorn.
2. Description of the Prior Art
Satellite communication is distinguished in wide coverage and terrestrial interference avoidance, and is widely used in military, probe, and commercial communication services, such as satellite navigation, satellite voice broadcasting, and satellite television broadcasting. A conventional satellite communication receiving device consists of a dish reflector and a low noise block down-converter with feedhorn (LNBF). The LNBF is disposed on the focus of the dish reflector, and is used for receiving radio signals reflected via the dish reflector, down-converting the radio signals to middle band, and then transmitting the radio signals to a backend satellite signal processor for signal processing, thereby enabling the playing of satellite television programs.
The LNBF is composed of a feedhorn, a waveguide and a low noise block down-converter (LNB). The feedhorn is used for collecting signals reflected by a satellite antenna to the waveguide, to output to the LNB. Except receiving satellite signals, the feedhorn can transmit signals (reflected via the dish reflector) to the satellite for different applications.
The reception quality of the satellite antenna is significant related to the placed position of the feedhorn. For example, the feedhorn radiates electromagnetic waves from a focal position of the satellite antenna, and thereby the electromagnetic waves are reflected to the satellite via the dish reflector. A number of signals that can be received by the satellite antenna is decreased when the feedhorn is deviated from the focal position. In practice, the focal position is represented by a focal length to diameter ratio (F/D) of the dish. Note that, the reception efficiency of the satellite antenna is affected by whether the focal length to diameter ratio (hereafter called F/D value) of the dish matches a beamwidth formed by the feedhorn. In other words, different F/D design requires different values of the beamwidth, so that the beams emitted from the feedhorn can be efficiently received by the satellite antenna. For example, a dish with F/D=0.6 requires a narrower beamwidth compared to a dish with F/D=0.4. If the beamwidth does not conform the F/D design of the dish (e.g. too wide or too narrow), reception efficiency of the satellite antenna is affected, thereby lowering the reception quality of the satellite antenna.
However, a device for adjusting the beamwidth formed by the feedhorn has never been provided in the current market, so that the beamwidth formed by the feedhorn may not match the dish perfectly. In addition, in the beginning of product design, manufacture companies take much effort to reduce size of products, toward compact products and low cost. Therefore, under reduction of an opening size of the feedhorn, how to match the beamwidth and the dish is a topic for discussion.